Idea for Minigun.

The spreading decreases after the 1st hit or kill (?plus xN speed of shooting ?)

Idea for Medigun

The closer to the mate, the faster it heals. Or vice versa.
Just an idea.

"Sentries's Fault".

Disguise Kit that attract Sentries' attention to you, though they don't shoot.
Maybe, it works only few seconds.

Just an idea, needs more thinking.

/to be continued.../

Different Trajectory for the Pipes.

The old one is /\. The one I suggest is \/, i.e. it goes down, firstly, then it flies up.
New grenade launcher, probably.

Mechanics for the Rocket Launcher.

Next shoot only after the previous rocket has been exploded.